feat(configurator): server-side surface area calculation from STL

Add trimesh-based surface area calculation for uploaded STL files:
- New /fp/configurator/calculate_surface_area jsonrpc endpoint
- action_calculate_surface_area() method on fp.part.catalog
- "Calculate from 3D Model" button visible when a 3D model is attached
- Returns area in sq in (converted from mm2), vertex/face counts,
  and bounding box dimensions

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

fusion-plating/fusion_plating_configurator/controllers/__init__.py

@@ -0,0 +1,2 @@
+# -*- coding: utf-8 -*-
+from . import configurator_controller